Atheists can be ethical, but not "moral." Moral implies accession to a higher authority, and moral imperatives often involve behavior that is not overtly harmful (e.g., lust, greed, hatred), and their ethics only kick in when actual, demonstrable harm is imminent or visible.
A Moral person abhors abortion even while acknowledging that the beginning of "personhood" is in question. It is the mere possibility that abortion kills a person that makes it morally unacceptable.
The Ethical person sanctions abortion, as long as the personhood of the fetus cannot be demonstrated.
Huge difference.